The aim of this project is to study the reflex mechanisms and the neural pathways involved in pulmonary reflexes. It will link previous and current research efforts of the principal investigator on J receptor reflexes with reflexes from other pulmonary afferents. One of the goals of this project in the first three years (currently in its third year) was to study these pulmonary reflexes in the newborn and at different ages of development. The first step of this work relating to the status of the J receptor reflexes in the newborn has been completed and published. It is now necessary to study the development of the neural pathways involved in pulmonary reflexes, an aspect that has escaped attention so far. This will be the first attempt made to study the neurophysiology and neuroanatomy of the brain stem respiratory centers in the neonate and to relate these findings to the genesis of different patterns of breathing and respiratory reflexes. Currently, ongoing research by the principal investigator on J receptor reflexes has focussed on the use of physiological stimuli - pulmonary congestion and edema as a mechanism to stimulate J receptors in the adult animal. This is the first time an attempt has been made to study the manner in which these reflexes operate under physiological conditions. This phase of the project is currently in a preliminary stage and will be developed fully in the next few years. In this project, a considerable emphasis will be placed on motor inhibition from pulmonary receptors. It is proposed to record from central respiratory neurons using conventional neurophysiological techniques and then locate the central pathways of these centers with recently developed neuroanatomical techniques of retrograde transport of horseradish peroxidase and autoradiography. The principal investigator is interested in vagal afferent and central respiratory interactions and will be involved in assessing the relative role played by different pulmonary receptors in various pulmonary reflexes. In essence, this project addresses the question: How do vagal afferents exert their influence on respiratory mechanisms and motor systems and where is this information processed?